Abrasive jet systems that produce high-velocity, abrasive-laden fluid jets for accurately and precisely cutting various materials are well known. Abrasive jet systems typically function by pressurizing water (or another suitable fluid) to a very high pressure (e.g., up to 90,000 pounds per square inch (psi) or more) by, for example, a high-pressure pump connected to an abrasive jet cutting head. The pressurized water is forced through an orifice at a very high speed (e.g., up to 2500 feet per second or more). The orifice forms the water jet. The orifice is typically a hard jewel (e.g., a synthetic sapphire, ruby, or diamond) held in an orifice mount. The resulting water jet is discharged from the orifice at a velocity that approaches or exceeds the speed of sound. The liquid most frequently used to form the jet is water, and the high-velocity jet may be referred to as a “water jet,” or a “waterjet.”
Abrasives can be added to the water jet to improve the cutting power of the water jet. Adding abrasives to the water jet produces an abrasive-laden water jet referred to as an “abrasive water jet” or an “abrasive jet.” To produce an abrasive jet, the water jet passes through a mixing region in a nozzle. The abrasive, which can be under atmospheric (ambient) pressure or pressurized in an external hopper, is conveyed through a meeting orifice via a gravity feed or a pressurized feed from the hopper through an attached abrasive supply conduit to the nozzle. A quantity of abrasive regulated by the meeting orifice is entrained into the water jet in the mixing region. Typical abrasives include garnet and aluminum oxide. Generally, the maximum diameter of individual abrasives should be no greater than approximately one third of the internal diameter of the abrasive supply conduit to prevent bridging of two particles, which can lead to clogging of the abrasive supply conduit. The abrasives can have grit mesh sizes ranging between approximately #36 and approximately #320, as well as other smaller and larger sizes.
The resulting abrasive-laden water jet is then discharged against a workpiece through a nozzle tip that is adjacent to the workpiece. The abrasive jet can be used to cut a wide variety of materials. For example, the abrasive jet can be used to cut hard materials (such as tool steel, aluminum, cast-iron armor plate, certain ceramics and bullet-proof glass) as well as soft materials (such as lead). A typical technique for cutting by an abrasive jet is to mount a workpiece to be cut in a suitable jig, or other means for securing the workpiece into position. The abrasive jet can be directed onto the workpiece to accomplish the desired cutting, generally under computer or robotic control. It is generally not necessary to keep the workpiece stationary and to manipulate the abrasive jet cutting tool. The workpiece can be manipulated under a stationary cutting jet, or both the abrasive jet and the workpiece can be manipulated to facilitate cutting.